(Chilkat2-Python) Generate Encryption Key

Discusses symmetric encryption key generation techniques for block encryption algorithms such as AES, Blowfish, and Twofish, or for other algorithms such as ChaCha20.

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import chilkat2

# Symmetric encryption algorithms are such that the encryptor and decryptor
# share a pre-known secret key.  This could be a "single-use" key that is 
# derived from a secure key exchange algorithm using RSA, ECC, or Diffie-Hellman,
# or it could be a password known to both sides, or
# it could simply be the binary bytes of the secret key known in advance on both
# sides.

# A secret key has no structure.  It's nothing more than N bytes of data.
# It should typically be random data, or bytes that resemble random data such
# as the hash of a password.

# The number of bytes in the secret key defines the bit-strength of an encryption
# algorithm.  For example, AES with a 32-byte key is 256-bit AES.  Most algorithms
# define restrictions on key sizes.  For example, AES has 3 choices: 128-bit, 192-bit,
# or 256-bit.  In the ChaCha20 algorithm, the key size must always be 256-bits (32-bytes).

# Both sides (encryptor and decryptor) must be in possession of the same secret key
# in order to communicate.   Whichever side generates the key, it must somehow
# deliver the key to the other side beforehand.  Key exchange algorithms, such as RSA, ECC,
# and Diffie-Hellman define secure ways of exchanging symmetric encryption keys.
# They do so using asymmetric encryption algorithms (public/private keys).  It is not
# required to use a key exchange algorithm to achieve the goal of having both sides
# in possession of the same secret key.  A long-living secret key could be exchanged
# via any secure out-of-band means.  For example, exchanging the information over a secure
# TLS (HTTPS) or SSH connection...

# This example assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

crypt = chilkat2.Crypt2()
crypt.CryptAlgorithm = "aes"
crypt.KeyLength = 256

# Generate a 32-byte random secret key,
# and use it in the crypt object.
prng = chilkat2.Prng()
secretKeyHex = prng.GenRandom(32,"hex")
# It is important that the number of bytes in the secret key
# matches the value specified in the KeyLength property (above).
crypt.SetEncodedKey(secretKeyHex,"hex")
print("randomly generated key: " + secretKeyHex)

# Alternatively, a password could be hashed using a hash algorithm
# the results in the desired key length.  Our desired key length
# in this case is 32 bytes, so we wouldn't want MD5 (16 bytes),
# nor would we want to use SHA-1 (20 bytes).  SHA256 would be the
# hash of choice because it results in 32-bytes of random-looking
# key material.
crypt.HashAlgorithm = "SHA256"
crypt.EncodingMode = "hex"
secretKeyHex = crypt.HashStringENC("mypassword")
crypt.SetEncodedKey(secretKeyHex,"hex")
print("password-based key: " + secretKeyHex)